Oil tank and method of storing oil



Sept. 1A5, 1931. E. M. CLARK OIL TANK AND METHOD OF STORING OIL Filed Sept.

fafa/72 /12 (Zar/Y Patented Sept. 15, 1931 UNITED STATES PATENT OFFICE EDWIN M. CLARK, OF CLARKSTON, MICHIGAN OIL TANK AND METHOD OF STORING OIL Application led September 12, 1927. Serial No. 218,995.

due to expansion and contraction, or other causes.

It is well known in the oil industry that enormous losses result from evaporation of stored oil, primarily during storage of the oil in large tanks at the oil fields, refineries, or distribution centers. Efforts have been directed along various lines toward elimination or reduction of such losses but no complete solution of theproblem has been heretofore achieved.

It is an object ofthe present invention to so improve the tanks employed for quantity storage of oil as lto completely eliminate all evaporationflosses.

In attaining this object, the invention contemplates extending a `water-filled trough Within and around the upper portion of an oil tank, and extending freely into said trough an annular ange marginally formed upon a cover for the tank.

The invention further contemplates es-i tablishing a liquid-full condition beneath said cover by maintaining a suiicient depth of water beneath the oil to raise the latter to the level of the cover.

It is an additional object of the invention, toprovidean oil' outlet beneath and adjacent lto said cover and to provide means for companying drawings, wherein:

Figure 1 is a vertifal sectional view of the improved tank, showing the cover in its nor.-

mal position seating uponv the trough, they illustrated levels of oil and water being such as to balance the hydrostatic pressures of a layer of Water upon the cover and of a small quantity of oil rising in the gauge well carried by the cover.

Figure 2 is a fragmentary'sectional view of the upper portion of the tank showing the conditions prevailing when the weight of the cover as Well as the pressure of a Cul layer of water thereupon are counter-balanced by the oil.

Figure 3 is a view similar to Figure 2 but showing the conditions prevailing when sufficient oil has been introduced in the tank to raise the cover some distance.

In these views the reference character 1 designates an oil tank which may be formed of sheet steel or other suitable metal, as is common practice. Ordinarily this tank will be cylindrical and open-topped and proportioned to store a large quantity of oil.

Interiorly mounted upon the upper portion of the tank 1 is an annular plate 2, the

vertical dimension of which may approximate three feet. Said plate is spaced several inches from the tank Wall, and has its lower portion out-turned and secured to saidwall, forming with the latter an annular opentopped trough 4 of considerable depth as compared to its radial dimension or width. The top of said trough is located some distance (as for example eighteen inches) below the upper edge of thc tank. Above said trough a. vertically adjustable cover 5 extends A substantially fully across the tank and a flange 6 rigidly carriedby said cover at its margin depends into said trough and is `vertically dimensioned to closely approach orA engage the bottom of the trough when said cover lies close to or engages the trough wall 2. The cover 5 is preferably flat or. nearly so and may be formed ofsheet iron or the like, reinforced if desired, in any suitable manner (not shown).

Suitably carried by said cover, preferably near the margin thereof, is a tubular gauge well 7 opening at its lower end through the cover and rising above the latter a suitable distance, as for example, several feet. The upper end of said gauge well is provided with a cover 8 which preferably has a marginal depending flange 9 freely engaging in an annular trough 10 carried by the upper tively for the iniiow of air to said well and 'its outflow therefrom.

An -oil delivery pipe 14enters the lower portion of the tank, passing preferably through the side wall thereof, and is valved as indicated at 15 exterio'rly of.v the tank. Branching from the pipe 14 at the supply side of the valve 15 is an oil discharge pipe 16 which passes through the tank wall and rises within the tank to terminate in the top ortion thereof in a bell-shaped inlet 17. ISaid inlet is preferably positioned to have a slight clearance from the cover 5 4when the latter is in its lowermost or'normal position, (see Figure 1). A valve 18 suitably7 located in the pipe 16 controls the out-flow of oil therefrom. l

Water from any suitable source of supply is adapted to be delivered into the tank adjacent to the bottom thereof through al pipe 19, and a branch 20 from said pipe rises eX- teriorly of the tank and extends across the edge of the latter to provide for a discharge of water upon the cover 5. A three-way Y valve 21 is arranged at the juncture of the pipes 19 and 20 to selectively control the delivery of water to the lower portion of the tank or upon the cover 5.

It is preferred to provide within the tank an annular curtain 22 suspended from the cover 5 and spaced slightly inwardly from l the plate 2. Said curtainmay be formed cfa closely woven fabric or other suitable sheet material and extends downwardly a distance preferably from ten to fifteen feet.` If desired a valved outletv 23 mayv connect". with the top portion of the tank through the side wall thereof providing for withdrawal of water from above the cover 5 and it may also be desirable-to provide a valved tting '.24 opening from the bottom of the trough 4 as a provision for washing out any accumulation of sediment. Itis option-al furthermore in-practicing the invention to provide a spillway 25 at the upper edge of the tank.

It may be necessary, in applying the invention to tanks of quite large diameter to provide means within the tank. for supporting the central portion of the cover, at such I times as this function is not exercised by the liquid below the cover. Thus pillars 126 may rise at .suitable points from thetank bottom to terminate at their upper ends substantially at the level of the upper edge of the plate 2.

In use ofthe described construction, water is pumped through the pipe 19-tol form the usual water cushion 27 in the bottom portion of thetank, and oil is then pumped in through the pipe 14, preferably to some lower level than that of the cover. lVater is now delivered through the pipe 20 on top of the cover member from which it discharges into the trough 4 filling the latter and overflowing therefrom to fall through the oil and add itself to the water cushion supporting the oil. Thus the oil level is raised, and eventually rises into the gauge well 7, thereby rapidly building up a liquid-static pressure in the entire body of oil, until this pressure becomes adequate to stop the flow of water across the upper edge of the annular plate 2. vAfter this occurs, water can he accumulated upon the cover 5, and this accumulation is preferably continued to a depth of atleast several inches. A trivial quantity of additional water will discharge from the trough, due to the accumulation of waterupon the cover and will further slightly raise the oil level in the gauge well to balance.

The tank lis now in readiness for storage of its oil content for any desired period of time positively without loss by evaporation. The prevention of evaporation necessarily follows from the liquid-full condition of the tank and from the fact that a protective layer of water lies always above the cover-5 and within the trough 4 forming a seal against access of air to the oil. The onlyv attention required to continuously avoid all evaporation is that necessary to maintain some depth of water upon the cover 5, since this water will of course, gradually evaporate and will furthermore, when the cover 5 rests upon its bearings, discharge through the trough into the bottom portion of the tank to such extent as the oil undergoes shrinkage or is withdrawn from the tank.

When it is desired to withdraw oil from the tank, the valve 18 is opened, permitting such outflow as may be desired through the pipe 16. -It is preferred t0 compensatev for any withdrawal of oil by pumping upon the cover 5 a corresponding quantityV of water, thus maintaining a liquidefull condition. It is, however, feasible to temporarily operate the tank on a part-full basis, owing the oil in and out by way of the pipe 14 as in the present l Subsequent to balancing the oil and water pressures against each other on initial filling of the tank, as hereinbcfore described, any

lvolumetric increase in the tank contents,

whether due to thermal expansion or an addi- ,tion of oil or cushioning water, will find relief by a flow of oily into the trough 4. The

- stantly attain.

level of water in said trough, inwardly of the flange '6, will consequently be lowered, the water so displaced effecting a slight increase in depth of the water upon the cover.

As the volumetric increase continues and the annular meeting plane of oil and water .progressively lowers in the trough, there is gradually built up in the oil a liquid static pressure, dueto the difference in densities of the contacting bodies of water andI oil. This gradually rising internal pressure ini the oil body is productive of and accompanied by a corresponding rise of oil in the gauge well 7. Eventually, internal (or liquid static) pressure of the oil reaches a magnitude such that its upwardly acting component equalizes the weight of the cover. i

When the conditions above described are fulfilled any further expansion of the tank contents acts to lift the cover 5. Such lifting however, does not involve any appreciable increase in the liquid pressure acting thereagainst, since the upward movement of cover 5 is responsive to a pressure-only slightly exceeding the weightof. the metal comprising said cover.

When the cover 5 is lifted as described the pressure of water in the trough at the outer \the dividing line above the top of the trough 4, then all water above the cover 5 will ow through the trough 4 to fall to the tank bottom. After such flow of water a balance of pressures between the thereby reduced water pressure and increased oil pressure will in- To correct this condition water may be withdrawn from the tank bottom and replenished upon the cover 5.

The term oil as herein employed, is considered inclusivev of any liquid petroleum roduct.

At times when cumulative expansion of the tank contents has lifted the cover 501i' its bearings'the relatively small daily change in oil volume (by thermal cause) will relatively move the cover 5 vertically without appreciable movement of the liquid within the trough 4. At the lifting of the cover 5 the verticalcolumn of water between the ange 6 and the tank wall 1 is correspondingly elongated to maintain a pressure in balance with the oil head in the gauge well 7 The condition may sometimes arise that volumetric decrease of the oil body, resulting either from thermal contraction. or withdrawals, may not only permit the cover to seat upon the pillars 26 but may tend to lower thev oil-level clear of the cover. It is to be noted that such lowering of the oil level will not be permitted s o long as sufficient water remains in the trough to discharge downwardly -through the oil and compensate for the oil shrinkage or withdrawals by the resulting increase in the volume of cushioning Water below the oil.

` While it will be apparent that the illustrated embodiment of my invention herein disclosed are well calculated to adequately fulvfil the objects and advantages primarily stated, it is to be understood that the invention f tank for receiving a sealing volume of water, w

a vertically movable cover member disposed within the tank above said trough provided with a marginal depending flange freely engaging in said trough, means for discharging water into the tank upon said cover member, f-

an oil discharge pipe having its inlet disposed slightly below the normal level of said cover member, and means within said tank prohibiting a direct flow of water from said trough to the inlet of said discharge pipe.

2. In a device of the character described, the combination with an open-topped oil storage tank, of a trough for receiving a sealing volume of water extending interiorly upon and around the upper portion of said tank, a vertically movable cover member disposed within the tank above said trough and provided with a depending marginal flange freely engaging in the trough, means for delivering oil into the tank below the cover member, a discharge pipe for oil having its inlet arranged within the tank slightly` below the normal level of the cover member, and an annular curtain carried by and dependingl from the cover member betweenJthe trough and said inlet.

3. In a device of the character described,- the combination |with an open-topped oil storage tank, of a trough for receiving a sealing volume of water extending interiorly upon and around the tank at a distance bei low the upper edge of the tank, a vertically movable cover member for the tank arranged above said trough and provided with a marginal depending iange freely engaging in said trough, means carried by the tank for discharging water therein above said cover member, means for withdrawing oil from the tank at a level below and adjacent to said cover member, and a tubular member rising lli) l from said cover-and ope-ning atits lower eX- tremity through the cover.

4. In a device of the character described,

the combination with an open-topped oilv storage tank, of a trough extending interiorly upon and `around the upper portion of said tank for receiving a sealing volume of water,

a vertically movable cover member disposed within the tank above said trough provided with a marginal depending flange freely engaging in said trough, means for discharging v water into the tank upon said cover member,

an oil discharge pipe having its inlet disposed slightly below the normal level of said cover member, means within said tank prohibiting a direct ow of water from said trough to the inlet of said discharge pipe, and a tubularfreely engaging in the trough, means for def,

livering -oil into the tank below the cover member, a discharge pipe for oil having its inlet arranged within the tank slightly below the normal level of the cover member, an annular curtain carried by and depending from the cover member between the trough and saidy inlet, and a tubular member rising from said cover kand opening at its lower extremity through the cover.

` 6. The combination with an oil storagel tank, of a cover member for the contents o-f said tank, of non-buoyant construction and of a material exceeding in weight its displaced volume of oil disposed within said tank and vertically movable to compensate for volumetric changes in the contents of the tank, means within the tank for supporting said cover member in a lowermost position thereof, means for introducing oil into the tank below said cover member, means for introducing water into said tank above saidl cover member, and means for opposing the liquid-static pressures of the Water and oil, marginally of said cover member, to effect a building up of the liquid-static pressure of the oil, and a consequentraising of the cover member upon a predetermined volumetric lincrease of the oil.

7. The combination with an open-topped oil storage tank, of ,a cover member therefor freely vertically movable within said tank and marginally formed with a depending annular flange, an annular trough interiorly carried by said tank below its upper edge, and receiving said flange, means within the tank, other than said trough for supporting said cover member in a lowermost position -tank below said cover member, whereby upon a rise of suchv oil to the lowermost level of said cover member, it enters the trough between said flange and the inner wall of the trough, and Ameans for delivering water upon said cover member and thence intosaid trough, whereby the liquid-static pressures of the oil and water are opposed in said trough to compel a raising or lowering of the cover responsive toa volumetric increase or decrease inthe oil.

8. The method o-f sealing a body of oil within a tank against evaporation, and of providing for volumetric vchanges in said body, consisting in engaging the surface of said body by a freely vertically movable upon and around said cover member, andso confining a portion ofsaid water and a portion of said oil beneath the marginal portion of the cover'as to oppose a downward liquid static pressure of the oil to an upward liquid static pressure of the water.

9. The method of sealing a body of oil against evaporation within a tank, and of providing for volumetric changes in said body consisting in engaging the surface of said body by a freely vertically movable cover member, maintaining an annular body of water surrounding said cover member,` and .so confining a vportion of said water and a portion of said oil beneath the marginal portion of the cover as to oppose' a downward liquid static pressure of the oil to an upward liquid static pressure of the water.

10. The method of storing a body of oil in a tank, consisting in engaging the. topl surface of said body by a freely vertically movable cover member, maintaining a cushion of water within the tank beneath the oil, inter- .posing between the cover and the tank wall -cover member,- maintaining a body of water 1l. A method of sealing a body of oil With- I in a tank against evaporation, and of providing for volumetric changes in said body consisting in engaging the surface of said body by a freely vertically movable cover member `maintaining a body of water in surrounding relation to said cover member, confining a portlon of said water and a portlon of sald oil beneath the marginal portion of the cover so as to oppose a downward liquid static pressure of the oil to an upward liquid static pressure of the water, and elevating a rela- 'tively small portion of the main oil body responsive to volumetric increase of the oil bod 13. The method of sealing abody of oil within a tank against evaporation, and of providing for volumetric changes in 4said body consistin \in engaging the surface of said body by a reely vertically movable cover member, maintaining an a nular body of water surrounding the covemember, superposing an annular water blanket upon the cover member and upon said annular body of Water, and applying to said body yof oil the joint hydrostatic pressure of said annular water body and of the superposed` blanket to counterbalance the weight of said cover.

14. The method ofsealing a body of oil 'within a` tank against evaporation, and of' providing for volumetric changes in said body consisting inengaging the surface of said body by a fareely vertically movable cover member, marginally carrying a depending annular flange, segregating an annular po'rtion of oil from said oil body inwardly 'of said flange, maintaining an annular water body in part outward of said flange, and in part inward of said iange and below the annular oil body, and subjecting the main oil body to a liquid static pressure transmitted from said'water body through said segregated portion of oil to the main oil body to counterbalance the weight ofsaid cover.

15. Ina device of the character described, the combination with an oil storage tank, of a cover member for said tank marginally formed with an annular dependingflange, a trough carried by the upper portion of the tank freely receiving said flange, and adaptedv to further receive a sealingbody of water,

\ means below said cover member for delivera wall surrounding'jsaid opening in-g oil to or withdrawing it from the tank,

means supporting said cover member in a lowermost position thereof, said cover member being formedl with an opening, and

and affording a portion' of the oil a rise above the cover member adequate to counterbalance the cover by resulting-hydrostatic pressure of the oil.

' 16. The method of storing a liquid within i a tank and safeguarding it against-evaporaltion consisting in applying a cover to the top surface of said liquid, maintaining a sealing body of ,a more dense liquid between said f cover and the wall of said tank, segregating a relatively small body of the lighter liquid from the main body thereof, in close proximity to said cover, and applying the gravityinduced liquid-static pressure of the heavier liquid to said main bodythrough the segregated portion of said stored liquid. v

17. The method of storing a body of oil within a tank, consisting in engaging said body by a freely vertically movable cover member, maintainin a cushioning body of water within the tan r beneath the oil, maintaining another and relatively lraised body of water adjacent to 'the cover member within the tank, isolated from said cushioning body, limiting down travel of the cover, and discharging water from said raised water body to said cushioning water body through the oil to maintain contact of the oil body with the cover, responsive to a volumetric decrease of the oil body, when the cover is in its lower limiting position.

In testimony whereof I sign this speciflcation.

EDWIN M. CLARK. 

